Seagrass scheme recruits citizens
Citizen scientists are doing Poseidon’s work in NSW.
Volunteers known as the ‘Storm Squad’ have been collecting seagrass fragments to successfully rehabilitate populations of NSW’s endangered seagrass, Posidonia australis.
The seagrass is key to the life cycles of local seahorses, blue swimmer crabs and snapper.
A study led by UNSW Science PhD student Giulia Ferretto and published in Biological Conservation, enlisted the help of 80 citizen scientists to restore Posidonia australis in Port Stephens.
“We launched Operation Posidonia – a collaboration between UNSW, Sydney Institute of Marine Science, the NSW Department of Primary Industries, and UWA – in 2018 and engaged over 5,000 people through our social media channels and guided seagrass meetings with local groups and high schools,” Ms Ferretto says.
“Over two years, our ‘army’ of volunteer citizen scientists – a ‘Storm Squad’ of beach goers, dog walkers and kayakers – collected a total of 1,500 naturally detached Posidonia shoots washed up on the beach after storms, strong winds and high tides.”
On good days, a one-hour beach walk could collect as many as 30 viable seagrass fragments.
The shoots were kept in large floating boxes before being replanted by divers in a variety of underwater locations, including the scars caused by boat mooring.
Ms Ferretto says most transplanted fragments produced new shoots after only a few months and are beginning to re-establish on their own, expanding in nearby areas.
The team is now expanding Operation Posidonia in Lake Macquarie and Botany Bay, two of the estuaries where Posidonia is formally listed as endangered.
The method of collecting washed up, naturally detached fragments of Posidonia (from heaps known as wrack), was adapted from an Italian study which used a similar species of grass.
“Posidonia [species] have an interesting distribution, they are only found in Australia and in the Mediterranean Sea,” Ms Ferretto said.
“The idea of using storm-generated fragments for restoration was initially developed by a group of scientists in Italy and applied to [their] local seagrass, Posidonia oceanica.
“We then combined this idea with the use of citizen science to speed up the collection of the fragments.”
Posidonia australis is a foundation species of seagrass which creates a complex and three-dimensional habitat that supports and sustains hundreds of other species.
The trouble is that Posidonia’s preferred habitat – clear waters and sheltered coves – is also the preferred habitat for recreational boating.
The traditional mooring of these boats, which involves a chain and concrete ‘block’ that harrows the seagrass bed, creates raw ‘sand scars’, which join up to form larger uninhabitable zones.
Some of these mooring sites around Port Stephens have been replaced by less destructive environmentally-friendly moorings. It is these sites that the team is restoring.
“The planting moment for me was the best part, especially when the marine life just started to swim around us divers,” Ms Ferretto says.
“There was one site, in particular, where every time we’d dive there, there was a group of cuttlefish following us from the moment we would jump in till the end of the dive, as if they were checking if we were doing a good job.
“Turning around after a long dive and seeing that patch that before had only sand now having beautiful green Posidonia leaves gave me a wonderful sensation every time.”